breaking wifi V10A

What can I do with breaking Wifi on experia V10A? WiFi connetion breaks very very often. With previous internet provider (telefort) I had Experia V10 and I had zero problems. Now I have changed to KPN on V10A and I cannot use WiFi. I have seen topics with that problem, and mostly problem is with that specific router. That is tragedy.
Please help.

Greetings
Slawomir